Coated-fine-aggregate, concrete composition and method

ABSTRACT

A concrete composition and method include a portion of fine aggregate bearing a coating of a polymer, which may be a continuous coating layer or a layer of powdered, discrete particles embedded in a binder. The polymeric coating may be a super absorbent polymer (insoluble in water, but absorbing water), or another polymer such as the acrylamides, co-polymers thereof, polyacrylamides, or the like (soluble in water). The coating absorbs water, but particles are too small to form significant voids. Water is absorbed into the concrete mix in far greater proportions (e.g. w/c ratio over 0.5) improving workability, doubling workability time, and improving ultimate compressive stress (strength).

BACKGROUND

1. Field of the Invention

This invention relates to concrete and, more particularly, to novelsystems and methods for formulation of concrete mixtures to improvemechanical and processing properties and characteristics.

2. Related Applications

This application is a divisional of U.S. patent application Ser. No.14/321,441, filed Jul. 1, 2014, which is hereby incorporated byreference.

This application also incorporates by reference U.S. Provisional PatentApplication Ser. No. 61/918,277, filed Dec. 19, 2013; U.S. ProvisionalPatent Application Ser. No. 61/531,042, filed Sep. 5, 2011; U.S. patentapplication Ser. No. 14/171,920, filed Feb. 4, 2014; U.S. patentapplication Ser. No. 13/599,735, filed Aug. 30, 2012; U.S. patentapplication Ser. No. 13/598,135, filed Aug. 29, 2010; U.S. patentapplication Ser. No. 13/418,227, filed Mar. 12, 2012; U.S. Pat. No.8,739,464, issued Jun. 3, 2014; U.S. Pat. No. 8,661,729, issued Mar. 4,2014; U.S. Pat. No. 8,510,986, issued Aug. 20, 2013; U.S. Pat. No.8,453,377, issued Jun. 4, 2013.

3. Background Art

Concrete is a common construction material. It is used for footings andfoundations routinely. It is sometimes used for walls of buildings orother walls for other architectural purposes. It is sometimes used forfloors and ceilings of buildings. It has been formulated over many yearsto include aggregate, cement, and water. It is typical in constructionthat higher ratios of water to cement will compromise the compressivestrength of concrete. Concrete has a comparatively little tensilestrength.

Meanwhile, reducing the ratio of water to cement creates challenges inthe workability of concrete. Typically, the ratio of water to cementinfluences a property called slump. Slump characterizes the tendency ofconcrete to flow down due to fluid in it rather than to stack up due toaggregate in it. Inasmuch as concrete is largely solid material,commonly called aggregate and constituted by coarse aggregate such asrock, gravel, or both, and fine aggregate constituted by some type ofsand, the solid materials may tend to stack if the cement iscomparatively thick or stiff. With more water, the cement fluid or“paste” formed by the wetted cement powder and added water tends tolubricate and separate the aggregate such that it will flow down to agreater extent.

Low ratios of water to cement tend to produce stronger concrete (greatercompressive stress before failure limits), whereas greater ratios ofwater to cement tend to delay setting up of the concrete, and therebyprovide improved ability to work the concrete, form it, surface treatit, finish it, and so forth. Also, more working time and better flowimproves the reduction of voids, the compacting or vibrating of theaggregate into place, the filling in by the cementitious fluid of cementand water among all the interstices, and so forth.

Concrete has various phenomena acting during its cure process. Curing isa chemical process whereby the cementitious fluid becomes a solid by thechemical reaction of water with the cement. Curing involves bothreaction of molecules of the cement with the water and with each otherto form bonds. It also involves a drying process whereby any excesswater may be evaporated away from the concrete.

During cure of concrete, the presence or absence of water may affect thecuring, cracking, strength, and so forth. For example, external surfacesmay tend to dry too quickly. This causes shrinkage and small cracks.Meanwhile, the internal portion of a concrete structure may take moretime, but may have insufficient water to complete the chemical reactionsthat are available with the molecules of the cement material.

Thus, two types of concrete curing are common. One is to provide a waterlayer over the concrete to maintain hydration at the surface and preventdrying during cure. Another is to rely on sufficient internal water,sometimes a comparatively excess amount of mixed in water, while alsocovering the concrete or sealing it against evaporation. Thus, onemethod is referred to as a wet cured concrete in which the surface ismaintained and moist. The other is called internal cure

It would be an advance in the art to provide a mechanism that couldimprove workability of concrete, without compromising its ultimatestrength. It would also be an advance in the art to provide water duringinternal curing. It would also be an advance to do so without leavingvoids of a size that creates stress concentrations and initiatesfractures. It would also be an advance to better seal againstperviousness, and reduce shrinkage and its associated stress, strain,and cracking in concrete.

BRIEF SUMMARY OF THE INVENTION

In view of the foregoing, in accordance with the invention as embodiedand broadly described herein, a method and apparatus are disclosed inone embodiment of the present invention as including a composition andmethod relying on a coarse aggregate, fine aggregate, cement, and atreated or coated fine aggregate portion. The fine aggregate may be anysuitable material currently used. The coarse aggregate may likewise besuitable larger pieces, such as gravel, rock, or both.

The coated fine aggregate may involve sand, of a suitable size, actingas a substrate and treated with a coating of a hydrophilic, polymericmaterial. The coating may be coated directly on the substrate as aliquid later dried. Instead it may be bound to a substrate by a bindersecuring a powder or dust made of a polymeric material such as anacrylamide polymer, polyacrylamide, or co-polymer acrylamide(collectively PAM) or the like. It may instead be made of any superabsorbent polymer (SAP).

A difficulty with the addition of polymers other than cement is the sideeffects. For example, it is known to use various plasticizers, hardeningchemicals such as chlorides that also act as curing accelerants, and thelike in order to modify the cure rates, strength, working properties,and so forth. However, although these additives modify the propertiesdesired, but often bring with them unwanted side effects. They oftensacrifice other properties (e.g., working time) that are sometimes asimportant as the preferred property (e.g., strength or hardness) thatthey improve.

The substrate may be coated with a binder that operates as a tackifier,adhesive, or the like. In some embodiments, the tackifier or binder maysimply be a solvent that partially dissolves the powdered polymermaterials or liquefied polymer material that will coated onto thesubstrate.

In some embodiments, the polymer may be barely adhered to the bindersecured to a substrate (e.g., sand). In other embodiments, the bindermay be of a comparatively thick tackifier, such as a material identifiedin any of the patent references incorporated hereinabove by reference.The binder layer may be a comparatively thicker or comparatively thinnerlayer. By thicker is meant that a significant portion, such as fromabout ¼ to about ¾ (or even from 10% to 90%) of the effective diameterof the polymer powder is actually embedded within the tackifyingmaterial or binder. In other embodiments, a solvent such as water,alcohol, or other solvent that will dissolve the powdered particles ofthe water-absorbing polymer may operate to dissolve a portion of eachpolymer and thereby form a binder to secure the particles to thesubstrate. Solvent and a portion of polymer may be premixed together asa binder, or simply interact on contact.

In some embodiments, in order to manage and otherwise manipulate therates of absorption, the operation of the water absorbing polymercoating the substrate, or the like, a shell or final layer may be formedover the top of the particles of the polymer once on the substrate. Thismay delay or slow hydration of the polymer or resist its separation fromthe substrate for a predetermined time established by the physicalproperties of the shell layer. The absorption rate of or access to,water may be used to control the water absorbing polymer. Again, liquidlayers, powdered layers, or a combination may be used to coat asubstrate. Several suitable materials and processes are disclosed in thereferences incorporated hereinabove by reference.

In one embodiment a composition comprising coarse aggregate, fineaggregate (substantially smaller than the coarse aggregate), cement, anda polymer coated aggregate is activated with water. The polymer coatedaggregate is a comparatively finely divided aggregate, and may besimilar to or the same as a portion of the fine aggregate. It may alsocome from another source. Sand of any masonry or concrete type may betypical, and may be washed to remove fines or to provide a consistentsize and ability to adhere a layer of hydrophilic polymer, either as a“painted on” (liquid, subsequently dried or cured) or a powder securedto a fine aggregate substrate.

Powder formed of a polymer may be selected from an acrylamide, anacrylamide co-polymer, a polyacrylamide (PAM), a super absorbent polymer(SAP), or other similar hydrophilic material. A binder may bind a powderto the substrate by any of several mechanisms including simple adhesionof a tacky substance, curing of a glue-like binder, partial dissolvingof the polymer and subsequent drying thereof, solvent binding by asolvent dissolving powder particles, solvent binding by a mixture of asolvent, such as water, and a polymer, such as an acrylamide, making acoating binder that readily forms an ionic bond with the dry powder whencoated thereon, or the like.

The cement, once mixed with water is constituted in a fluid flowable tolubricate the coarse aggregate and fine aggregate to an extent effectivefor pouring and casting the composition. Meanwhile, the polymer ishydrated by a portion of the water, which water is subsequentlyreleasable by the polymer, providing at least one of additional waterfor workability, water for reaction of cement chemistry, water forreduction of surface shrinkage, and slowing of surface or other dryingof the curing concrete.

In its cured state, the concrete has voids sized and spaced atrespective distances effective to maintain compressive strength at leastas high as that of the composition absent voids. Thus stressconcentrations, and gaps are minimized, improving concrete strength.

A target for the proportions of constituents may be about two partscement, about four parts fine aggregate, about four parts coarseaggregate, about 1.5 parts water, and about ten percent of the fineaggregate further bearing a coating of the polymer. In anotherformulation, the cement constitutes from about one and a half to abouttwo and a half parts, while the fine aggregate constitutes from about 3to about 5 parts, the coarse aggregate constitutes from about 3 to about5 parts, and water constitutes from about 1.25 to about 2 parts.

A method may include selecting a coarse aggregate, fine aggregate,cement, and a polymer. Thereupon, one may provide a coating on a portionof the fine aggregate, then mix the constituents with water. Casting themixture into a restraint such as a form or mold is effective to mold themixture to a shape.

The coating provides water effective to maintain fluidity of the mixturefor a period greater than one and a half hours, even more than doublethat, even 2 hours in certain tests. Thus the concrete is pourable andworkable much longer than conventional concrete. Moreover, the polymerreleases water for supporting complete reaction of the cement as itcombines with the water in a chemical reaction. Curing by the cementfrom a liquidous state to a solid state results in not only no loss instrength, but increased strength and increased volume, not only in theliquidous state, but also in the solid, cured state.

Although natural polymers may be used, such as gelatin, guar, and thelike, synthetic polymers as powders or very small spheres, having a meaneffective diameter substantially less than that of the fine aggregate,are available, cost effective, and serve well. Both soluble(acrylamides, co-polymers of acrylates and acrylamides, andpolyacrylamides) and insoluble polymers (SAP) work. Commercially, thereis some variation in referring to acrylic, acrylic acid, acrylamide, andthe like-based polymers, and it is found that polyacrylamide, aco-polymer or polymer of at least one of an acrylate, acrylic,acrylamide, acrylamide compounds, and the like appear to serve, as dovarious super absorbent polymers (SAP) of other types. Acrylamides, as aclass, tend to be soluble, while SAP materials, as a class, tend not tobe.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing features of the present invention will become more fullyapparent from the following description and appended claims, taken inconjunction with the accompanying drawings. Understanding that thesedrawings depict only typical embodiments of the invention and are,therefore, not to be considered limiting of its scope, the inventionwill be described with additional specificity and detail through use ofthe accompanying drawings in which:

FIG. 1 is a schematic image of a composition in accordance with theinvention embodied in a concrete;

FIG. 2 is a microscopic, cross-sectional view in schematic form of aparticle of coated fine aggregate illustrating several optional coatingconfiguration;

FIG. 3 is a schematic block diagram of a process for providing coatedaggregate for use in a formulation such as concrete or other fluid;

FIG. 4 is a schematic block diagram of a process for manufacturing orformulating concrete using a coated fine aggregate in accordance withthe invention;

FIG. 5 is a table illustrating results of testing of one embodiment of acomposition and method in accordance with the invention;

FIG. 6 is a chart illustrating data from testing of an alternativeembodiment of a composition and method in accordance with the invention;

FIG. 7 is a chart illustrating test results of material propertiescorresponding to a wet cured process;

FIG. 8 is a chart illustrating the material properties of a dry curedconcrete formed by a composition and method in accordance with theinvention;

FIG. 9 is a chart graphically illustrating the data for compressivestrength of the material of FIG. 8;

FIG. 10 is a chart illustrating permeability measured by absorption ofwater in a concrete composition formed according to a composition andmethod in accordance with the invention; and

FIG. 11 is a chart illustrating curves of strain in dimensionless unitsof length per unit length in a drying concrete sample from a compositionand method in accordance with the invention for a controlled, alightweight aggregate, and a coated fine aggregate composition.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

It will be readily understood that the components of the presentinvention, as generally described and illustrated in the drawingsherein, could be arranged and designed in a wide variety of differentconfigurations. Thus, the following more detailed description of theembodiments of the system and method of the present invention, asrepresented in the drawings, is not intended to limit the scope of theinvention, as claimed, but is merely representative of variousembodiments of the invention. The illustrated embodiments of theinvention will be best understood by reference to the drawings, whereinlike parts are designated by like numerals throughout.

Referring to FIG. 1, a composition 10 may be formulated, combined ormixed, and cast in a suitable containment such as a mold, form, or thelike to make an article, footing, foundation, structure, beam, buildingor portion thereof, or another structure. The composition 10 may existin a liquidous state, in a plastic state, or in a solid state. Byliquidous state is meant that the material will flow, notwithstandingits solid content. By a plastic state is meant that the material may bedisplaced without rupture or damage, often because it is notsufficiently solid to fracture. It may be in a solidous condition whereit has not been strained (either stretched or compressed) sufficientlyto cause permanent failure or fracture. By a solid state is meant thatthe composition has cured, the chemical reactions have occurred torender the liquid portions solid, and the overall material has a solidstructure.

The composition 10 may typically include a coarse aggregate 12. Suitablecoarse aggregate 12 is typically gravel, rock, or the like, as commonlyused in concrete. The composition 10 may also include various types offine aggregate 14. Fine aggregate 14 in concrete is sand. Sand comes invarious nominal “sizes” indicating an effective diameter or the like.

For purposes herein, effective diameter will be defined as that term isunderstood in an engineering context. Effective diameter is the diameterthat would exist if the entire perimeter were placed in a geometry thatwould cover the entire area. Thus, four times an area divided by thewetted perimeter is the hydraulic diameter or effective diameter. Thisworks out to be the diameter of a circle, cylinder, or sphere as thecross-sectional area, if the actual geometry of interest is purelycircular or spherical. This also works out to be the length of a side asan effective diameter if a geometry were exactly a square or cube. Thus,in the limit, an effective diameter of any cross-sectional area worksout to characterize the shape as if it had an actual diameter or lengthof a side. In any other shape the effective diameter is the valuedictated by the formula.

Thus, a coarse aggregate 12 may have an effective diameter that is manytimes, even a hundred times or more, larger than that of the fineaggregate 14. Meanwhile, the fine aggregate 14 may also have a range ofeffective diameters. Materials by nature and by processing do notnecessarily have a consistent effective diameter unless carefullysorted, which they may be in certain circumstances. Thus, the fineaggregate 14 may have a mean or average effective diameter. Everyparticular constituent piece or particle or granule of the fineaggregate 14 may also have its own effective diameter.

A cement 16 may be a cement of any particular type. For example, plasterof Paris forms a cement. Portland cement is another material commonlyused in construction that also operates as a cementitious material. Itbonds to itself, adheres to other materials, and mixes with water toform a chemical reaction that increases the weight of the cementitiousmaterial by bonding with the constituents of the water.

This chemical bond may be demonstrated by calcining a cement, concrete,plaster, or the like. Temperatures are elevated sufficiently high tobreak the chemical bonds, drive off the water constituent, and therebyreturn the cement powder to an unconsolidated, weak, and grindable, oreven powdered, state for reuse.

A certain fraction of the fine aggregate 14 may be set aside, or may beintroduced from another batch or type of fine aggregate 14. As apractical matter, a layer 18 may be coated on some or all of the fineaggregate 14. It has been found that an amount of from about one percentto about ten percent of the fine aggregate 14 may be produced asdiscrete granules 20 each coated with a layer 18. Thus, a coated fineaggregate 20 results. The coated aggregate 20 core may be identical tothe fine aggregate 14, or may come from a completely different source.It may have a different mean effective diameter, or the like.

Referring to FIG. 1, while referring generally to FIGS. 1 through 11,the composition 10 may be constituted as the coarse aggregate 12, thefine aggregate 14, the cement 16, the coated fine aggregate 20 with thelayer 18 applied to each granule 22, and water. In this configuration,the composition 10 is a liquidous material. It contains solids such asthe coarse aggregate 12 and the fine aggregate 14, as well as the coatedfine aggregate 20. However, it also includes water that is free andwater that is mixed or bound with the cement 16.

The portion of water, which is typically characterized by the ratio ofwater to cement 16, tends to fluidize or lubricate the interactionbetween the various aggregates 12, 14, 20 thereby promoting a pourablecomposition 10. Over time, the composition 10 may be poured into a shapedefined by a concrete form, pan, mold, or the like. It may be worked byworkmen, such as by augering, shifting, vibrating, settling, trowelling,or the like. It may be marked, imprinted, shaped, and so forth.

Over time, sufficient of the cement 16 will react with the water toreact by a consolidation of the molecules, constituents, within thecement 16. Thus, eventually, the material becomes a solid throughout.The cement 16 has hardened. Over time, water is used up in the chemicalreaction with cement 16, any remainder may be evaporated out and escapethrough the porosity of the composition 10 remaining, and so forth.

Referring to FIG. 2, while continuing to refer generally to FIGS. 1through 11, the coated aggregate 20, typically coated fine aggregate 20may be formed by a substrate 22 that is a particle or granule like thefine aggregate 14, or some other similar fine aggregate 14. In certainembodiments, the coated fine aggregate 20 may actually use a substrate22 of a lightweight aggregate. Lightweight aggregate may be thought ofas an organic material that tends to absorb water, or a highly poroussolid material that has sufficient capillary action to absorb and storean extra amount of water.

Coarse aggregate 12 does not typically absorb significant water. Somesmall amount of water may be attached to a surface, may coat a surface,or may embed in certain porosities. Typically very little water adheresto a coarse aggregate 12. Similarly, fine aggregate 14 does not absorbwater. However, light weight aggregate is selected to be porous, and maybe organic in order to absorb more water.

A substrate 22 may be coated by mixing with a binder 24. The binder 24may actually be a solvent 26 effective to dissolve a particularpolymeric material. Similarly, the binder 24 may be a tackifier 28. Itis not uncommon to speak of the binder 24 as a tackifier 28 or adhesive28. That is, binders 24 may be liquidous in nature and eventually cureto a solidous state. On the other hand, tackifiers 28 may also operatein a liquidous, typically quite viscous, condition to bind materials tothe substrate 22. However, tackifiers 28 may cure to a solid or maythicken yet not cure to solids. They may simply remain a very thick orviscous adhesive 28 that adheres.

Thus, a binder 24 may be a solvent 26, may be a mixture of a solvent 26with a dissolved material therein (as in the first quadrant of FIG. 2),may be a tackifier 28 or adhesive 28, or the like.

In the illustrated embodiment, four quadrants (of circles, starting atnoon o'clock) are shown for the substrate 22 as a granule 22. Thesubstrate 22 is shown with various embodiments of a polymer 30 which maybe constituted as a powder 32 (fine particles 32) each formed of apolymer 30 comminuted to a comparatively small (compared to theeffective diameter of a substrate 22) particle size. This particle sizemay be characterized as a powder 32 or dust 32. Such materials andprocesses are described hereinabove and in the references incorporatedherein by reference.

Certain embodiments of the coated aggregate 20 may be coated with ashell 34 or a shell layer 34 (see second quadrant) that actually coversthe particles 32 in order to delay or otherwise affect the access tothose particles 32 by water. Thus, a shell 34 or shell layer 34 maydelay activation of the layer 18 of a coated aggregate 20 by delayingthe access to water by individual particles 32 of a polymer 30.

In the illustrated embodiment, a shell layer 34 may be the same materialas the binder 24, the same material as a tackifier 28, the same materialas the polymer 30, or the like. The significance of the shell 34 is thatit is an engineered material that is applied in an engineered manner andmethod that will provide the amount of delayed desired. Thus, forexample, the shell 34 may slow the access to, or the rate of absorptionof, water by the layer 18.

It should be noted herein that reference numerals followed by trailinglowercase letters refer to specific instances of the item designated bythe reference numeral. Thus, it is proper to speak of a referencenumeral alone, or of a reference numeral with a trailing alphabeticalcharacter. The inclusion of any or all of the examples identified byreference numeral may be implied by the use of the reference numeralalone. The identification of a specific instance and example may beimplied by the use of a trailing alphabetical character.

In the illustrated embodiment, the four quadrants illustrate fourmethods and compositions for coating a layer 18 on a coated aggregate20. In the first quadrant moving clockwise from the noon position as ona clock face into the first quadrant, one sees an embodiment in which abinder 24 a is formed by a mixture of a solvent 26 a, and a polymer 30that coats the substrate 22 sufficiently long that adherence of thepolymer 30 as a particle 32 may be done first by surface tension andultimately by either bonding, dissolving, or both of the polymer 30 inthe particle 32. Thus, for example, a polymer 30 such as an acrylamide,typically polyacrylamide or a co-polymer acrylamides is soluble inwater.

Similarly, in the third quadrant, the solvent 26 a may be water adheredby capillary action to the substrate 22. Contact by a particle 32 of thepolymer 30 results in the polymer 30 adhering by the surface tension ofthe water solvent 26 a. Meanwhile, a portion of the polymer 30dissolves, forming a binder 24 that actually provides a chemical ionicbonding as in the mixture of the first quadrants. Thus, the binder 24 abecomes a layer not simply of water solvent 26 a, but of a mixture ofthe solvent 26 a and the polymer 30.

In the first quadrant, the dashed lines illustrate that the actualboundary of the particle 32 becomes uncertain, as the polymer 30 maydissolve and flow even to contact the surface 21 of the substrate 22.

The second quadrant or the afternoon or three-to-six o'clock regionillustrates an alternative embodiment for creating the layer 18. In thisembodiment, the particle 32 of polymer 30 is a material that may becompletely different in chemical constitution from a solvent 26, fromthe material 30, and the like.

For example, this stands in contrast to the first quadrant. That solvent26 a may actually be a mixture of the chemical of the polymer 30, andwater or other solvent 26 a. Thus, alcohol, water, or the like, as asolvent 26 a for the polymer 30 may be mixed with a portion of thepolymer 30 until the polymer 30 is dissolved therein. This may form acoating as the solvent 26. Thus, the speed of ionic bonding to theparticle 32 of polymer 30 may be greatly enhanced by premixing a solvent26 a with a portion of the polymer 30, until the polymer 30 isdissolved, and thus forms a cohesive bond immediately with the particles32, after which it partially dissolve the particles 32, forming thelayer 18.

In contrast, the binder 24 b is a comparatively thicker layer, that willtypically extend from ten to 90 percent, and usually from about ¼ toabout ¾ of the effective diameter of the particles 32. Thus, theparticles 32 may embed in the binder 24 b such that the tackifier 28 bconstituting the binder 24 b actually seeps around, and absorbs withinit a significant fraction of, the geometry of each of the particles 32.

Also in the second quadrant is illustrated a shell 34 coating thetackifier 28 b as well as the particles 32 of the polymer 30. In theillustrated embodiment, the shell 34 may be solid, rigid, or a fluid. Itis typically better that the shell 34 be comparatively solid or rigid(not tacky) such that it does not operate as an agglomeration adhesiveto agglomerate the particles 32 together. It is best that the coatedaggregate 20 remain as discrete particles 32 for purposes ofdistribution in the composition 10.

Referring to FIG. 2, and specifically looking at the third quadrant, atackifier 28 or adhesive 28 forming a binder 24 may typically be formedof a material that dissolves the particle 32. More properly, one may saythat the solvent 26 c coating the surface 21 of the granule 22 orsubstrate 22 dissolves on contact a portion of the surface 30 or polymer30 in the dust 32 or powder 32. The result is self adhesion by theparticles 32 against the surface 21. Typically, the preference in theembodiment in the first quadrant is that a certain portion of thetackifier 28 is solvent 26 a and another portion is dissolved polymer30. The preferred mechanism in the example of quadrant three is simply asolvent 26 c dissolving the polymer 30 as the particles 32 come incontact therewith.

Referring to the fourth quadrant of the illustrated embodiments, thetackifier 28 d operating as an adhesive 28 d merely contacts theparticles 32 of polymer 30 in a mixing process as described in detail inthe references incorporated herein by reference. Any suitable mixingprocess that will gain the desired effect is appropriate.

One concern in most embodiments is the issue of obtaining a sufficientlygood coverage by the particles 32 in order to render the tackifier 28 dineffective to agglomerate together distinct granules 22 of thesubstrate 22. This is typically done by virtue of a comparativelycomplete coverage of the tackifier 28 d by the particles 32 of thepolymer 30.

In the illustrated embodiment, the granules 22 adhere in sufficientlyhigh density of numbers that no appreciable amount of the tackifier 28 dacting as a binder 24 d can make contact between granules 22. Thus, thedusting of the powder 32 or particles 32 is itself an anti-adhesiontreatment of the tackifier 28 b acting as a binder 24 b in the fourthquadrant embodiment.

Referring to FIG. 3, a process 40 may include setting up 41 orpreparation 41 for a coated fine aggregate 20 or CFA 20. The setup 41may be followed by a manufacturing 42 of the CFA 20. In addition, oncemanufactured 42, the CFA 20 must be disposed of 43 and thus thedisposition process 43 may be undertaken.

One interesting observation is that a composition 10 in accordance withthe invention is only one use of the CFA 20. Other dispositions 43 arealso available and some are extremely useful such as soil amendments andfracking fluid additives as well as drilling mud additives.

Referring to FIG. 3, while continuing to refer generally to FIGS. 1through 11, the setup 41 or preparation 41 may include selecting 44 asubstrate 22. Selecting 44 may involve certain engineering calculations,reference to standard practices, and the like. As a practical matter, ithas been found that a washed sand forms a good substrate 22.

Likewise, it may be advisable as part of the washing, or as a separateprocess to sort or sieve the substrate 22, in order to provide a moreconsistent effective diameter thereof. Thus, to maintain a higherfraction of the overall supply of the substrate 22, sized closer to themean value of effective diameter may be advisable. However, this is notnecessarily required. It does provide for a certain amount ofconsistency.

Selecting 45 the binder 24 is related to selecting 44 of the substrate22 primarily in that the binder 24 should be compatible. In certainembodiments, for example, the substrate 22 may be an organic materialmeaning a biological material rather than an inorganic or rock (e.g.,inorganic, non-degradable, or other non reactive product).

Selecting 45 the binder 24 is also dependent upon the mechanism forbinding as described with respect to FIG. 2 above. Depending on thenature of the polymer 30 that will constitute the particles 32 or powder32, certain binders 24 may simply not be effective. For example, if aSAP polymer 30 is used, then the binder 24 should be selected to beadhesive in nature as a tackifier 28. This is because the SAP 30 willtypically not dissolve in water. Thus such phenomena may not be reliedupon to create the binder 24, or tackifier 28 to include SAP as binder24. On the other hand, some materials 30 may actually have a solvent 26other than water that may be used as a binder 24 or to create a binder24. Once evaporated, it will then leave the particle 32 adhered to thesubstrate 22, to thereafter interact with water by absorbing it.

Selecting 46 a polymer 30 is a matter of engineering design. Forexample, the type of polymer 30, its processing, its ability to becomminuted or manufactured at a suitable effective diameter, and thelike may all be considerations. Likewise, the amount of water that willbe absorbed by a polymer 30 is a significant factor in selecting apolymer 30. For example, materials that will absorb 10 times theirweight are available, but so are materials that will absorb manyhundreds of times their weight. In the contemplated embodiments, SAPpolymers, which have been shown to be damaging to the materialproperties, specifically the mechanical strength properties, of concretecompositions 10, are often not suitable in their manufactured form.However, by selecting smaller particles or by manufacturing smallerparticles, a powder 32 having a mean effective diameter that is withinthe range of from about one hundred to about three hundred microns, andtypically targeting at around one hundred fifty microns in effectivediameter have been found suitable. Smaller sizes also work, thus sortingmay be done simply by a sieve process that removes overly large or smallparticles 32 from a supply of the polymer 30.

Thus, selecting 46 a polymer 30 may be done in a way that effectivelydefines the thickness of a layer 18 surrounding a substrate 22.Likewise, obtaining suitable coverage, to resist agglomeration of theparticles of substrate 22 to itself or to other granules 20, 22 thereofis important for application and for disposition.

Providing 47 plant and equipment may be done in any suitable manner.Again, the references incorporated herein by reference identify somespecific instances of equipment, process parameters, and so forth bywhich suitable CFA 20 compositions may be made. Thus, mixers, grinders,feeders, dryers, and so forth may be purchased, connected, and otherwiseconfigured for executing a process to combine the substrate 22 with abinder 24 constituted by a solvent 26, tackifier 28, or some combinationthereof.

Likewise, if a shell 34 is to be added, then such may be accommodated.Meanwhile, handling the particles 32 of polymers 30 alone, duringcoating processes for the substrate 22, and thereafter may also beengineered into the provision 47 of the plant and equipment necessary toconstitute the CFA 20.

Likewise, a composition 10 may require its own plant and equipment.However, in currently contemplated embodiments, conventional equipmentfor use in the compounding of concrete compositions 10 may be used ascurrently constituted. In certain embodiments in the CFA 20, no changein the formation of a concrete composition 10 is required by way ofequipment, or the like. That is, no significant change that is notalready available is necessarily required.

However, certain steps may be done in a different way, or to a differentextent in compounding a concrete composition 10 in order to provide thebenefits in accordance with the invention. Thus, more water may beadded, and different constituents may be modified. However, thosechanges do not require (in certain presently contemplated embodiments)any change in the plant and equipment involved in mixing the composition10 or handling it in its application

Manufacturing 42 the CFA 20 may include applying 49 a tackifier 38,solvent 26, both, or other constituents to act as a binder 24.Thereafter, applying 50 a polymer 30 may involve adding a dust 32 orpowder 32 as individual particles 32 adhering to the binder 24 and thuscoating the granules 22 of a substrate 22.

In alternative embodiments, the polymer 30 may be painted 52 on orotherwise coated 52 as a liquid. It may be cured or dried rather thanadhered as a dust 32 or powder 32 coating the binder 24 on the substrate22.

Finishing 53 may involve adding a shell 34 or outer layer 34 over theparticles 32 of the polymer 30. Similarly, a shell 34 may actuallysurround a coating painted 52 or coated 52 on as a liquid over thesubstrate 22. Meanwhile, dusting 51 the powder 32 of particles 32 hasbeen found a suitable mechanism and one that provides ready separationof the individual granules 22.

It has been found, however, that using a mixture of a solvent 26 and apolymer 30 provides a suitable binder 24 to receive a dusting 51 ofparticles 32 of a polymer 30.

It has also been found effective that a tackifier 28 that iscomparatively thicker, as illustrated in the second quadrant of FIG. 2,is also effective in certain embodiments for maintaining adherence ofthe particles 32 or powder 32 against the substrate 22. In otherembodiments, where release of the powder 32 is desired, than acomparatively thinner layer of the binder 24, and typically embodied asa tackifier 28, may serve to render the particles 32 separable orstrippable from the tackifier 28 at a point after hydration.

Curing 54 may involve drying. Drying may be done in a drying tower asfalling granules 20, 22 drift down in an upward, drying flow of air.Curing 54 may also come as a chemical reaction coming to completion.Regardless, curing 54 is primarily a matter of stabilizing the granules22 with their coating of the polymer 30 either as a dusting 51 ofparticles 32, a liquid coating 52, solidified, or otherwise.

Managing 55 the CFA 20 may involve packing, storing, transporting,refrigerating, drying, protecting, and otherwise maintaining thestability of the CFA 20. Warehousing may involve protection from heat orhumidity, providing suitable aeration, maintaining free from changes inhumidity, sealing the CFA 20 against the incursion of local humidity orrain, and so forth. Thus, managing 55 the CFA 20 maintains itsconsistency, composition, and its operability in the future as a usefulconstituent in a composition 10 or otherwise.

The disposition 43 of the CFA 20 may involve formulating 56 acomposition 10. Formulating may involve determining proportions,effecting actual mixing, or the like. Formulating 56 is a term that isoften used to simply mean the design of a composition 10. In other uses,the expression of formulating 56 may involve the actual mixing togetherof the constituents constituting a composition 10. By either, or both,the proportioning, mixing, rates thereof, and so forth may be selectedand accomplished.

For example, in certain embodiments, such as a process for compounding acomposition 10, water may be added at different times in differentquantities. In fact, a composition 10 using the CFA 20 as a constituentthereof may still be cured as a wet cured concrete or a dry curedconcrete. Wet curing indicates that the surfaces are maintained damp oreven fully wetted or inundated.

In other embodiments, the dry curing indicates that the outer surface isnot wetted, although it may be protected, sealed, or otherwiseconfigured to resist excessive drying or an excessive drying rate. Thus,the water in the composition 10 at the surface thereof is not undulyprejudiced by evaporation or the loss of liquid needed for compoundingwith the cement 16 itself.

Applying 57 may involve molding, pouring, casting, or otherwise applying57 the composition 10 to a particular utility. Forming pillars, posts,sidewalks, footings, foundations, walls, floors, and so forth may allinvolve application 52 of a composition 10. One benefit of an apparatus,method, and composition in accordance with the invention is that the CFA20 is adaptable to many uses without requiring changes in the equipmentor the process steps for using that equipment.

Moreover, it has been found that working times or workability durationshave been greatly extended. For example, in certain examples, a controlprovided only about 1½ hours of total working time. Only during thattime could a composition 10 (absent the CFA 20) still be effectivelyworked without damage to its properties, structure, or the like. Incontrast, that time was extended by an additional 2 hours by use of theCFA 20 as a portion of the fine aggregate 14.

Resolving 58 may involve one or more of several processes.Notwithstanding the description herein of concrete design, formulation,mixing, and application 52, the CFA 20 may also be applied 57 in otherapplications.

For example, Applicant has found in certain examples and tests that oneapplication 57 is as a material 24 placed in the earth as a soilamendment, as a seed treatment, as a seed operating as a substrate 22,and the like. Moreover, the CFA 20 has been found to operate as anexcellent proppant and as an introductory material for fracture fluidsto provide additives instantly mixing thereinto.

Also, for example, with the deep layer (comparatively deeper tackifier28) of the second quadrant of FIG. 2, material has been found to be anexcellent proppant that travels well into a formation served by a wellbore before acting. Similarly, by adding the shell 34 illustrated, evenfurther delays may be created in order to place proppants or thesubstrates 22 as proppants well into a formation deeply and distantlyfrom their point of introduction.

On the other hand, the lubricity and viscosity of such fluids have beenmodified readily by using the configuration of the third quadrant ofFIG. 2, wherein the particles 32 may be more readily accessible towater, hydrate more quickly, but nevertheless still entrain quickly andwell into a well bore fluid. Thus, such embodiments have been found toserve well for introducing additives with minimal mixing, directly intoa bore fluid.

In such embodiments, the adhesion of the particles 32 is not as durableas in that of the second quadrant. Thus, this characteristic of theduration of the particles 32 in adhering to the substrate 22 may beengineered. Similarly, according to the embodiments of the first andthird quadrants of FIG. 2, durability of a polymer adhesion to asubstrate 22 may be engineered, controlled, and used in application 57of the CFA 20.

Thus, resolving 58 may involve curing 58 of a concrete composition 10.In other embodiments, resolving 58 may involve the disposition of asubstrate 22 as a proppant. In other embodiments, resolving 58 mayinvolve the stripping of particles 32 after full hydration, or at somepoint during hydration to separate from the substrate 22 in order tomodify fluid properties.

Ultimately, operating 54 a system relying on the CFA 20 may involve oneof several or many of several options. For example, a concrete structuremay be put into operation 59 serving the structural needs of supportingloads, vehicles, or the like. Similarly, a concrete structure mayoperate 59 to act as a footing supporting a foundation, a foundation ona footing supporting a building, or a wall in a structure, such as abuilding, compound, machine, mounting surface, or the like. Thus,operating 59 may indicate any of the functionalities to which a CFA 20,a composition 10, either, or both may be put.

Referring to FIG. 4, a process 60 for compounding a concrete composition10 in accordance with one embodiment of the invention is illustrated asa series of steps. In one embodiment, specifying 61 parameters that willcontrol the composition 10 may involve parameters governing the finaloperation 59 of a concrete structure. Likewise may be imposed certainrequirements or parameters controlling the content of the composition10, its compounding, mixing, casting, or the like. Likewise, theselection of or compounding of a CFA 20 may also be involved inspecifying 61 the parameters that will control the composition 10.

Thus, in general, specifying 61 the parameters that will control a CFA20, its use in a composition 10, or the application 57, resolution 58,or operation 59 of that composition 10 may be engineered in thatspecification 61.

Thereafter, the equipment may be put into place for formulating,compounding, and applying such a composition. Providing 62 a largeaggregate may involve selecting such an aggregate at a particular size,size range, or median size. In certain examples, gravel is used. In manycommercial applications, rock from about a ¾ inch (2 centimeters) meandiameter to about a 3 inch (12 centimeters) size has been foundsuitable.

Providing 63 fine aggregate 14 may involve selecting mean diameter,conditions, such as washing, and the like to remove fine (e.g., dust),and so forth, as appropriate. Ultimately, providing 63 fine aggregate 14will require ordering, shipping, and the like in order to deliver thefine aggregate 14.

Providing 64 a coated aggregate 20 will typically be the provision 63 ofa coated fine aggregate 20. Coating larger aggregate is possible, but isnot particularly effective, risks larger void spaces, and defeats partof the purpose of distributing effectively throughout a composition 10 acomparatively small fraction of fine aggregate 14 embodied as coatedfine aggregate 20. Thus, providing 64 a CFA 20 may be done by any of themethods shown, and may be compounded by any suitable method as describedin the references incorporated herein by reference or other methods.

Providing 64 a coated fine aggregate 20 will typically be done beforethe fine aggregate 14 is added. It may be possible to add the CFA 20after the addition of the fine aggregate 14 of a composition 10 duringmixing. However, it also provides additional distribution of the CFA 20by mixing the CFA 20 into the fine aggregate 14, before any fineaggregate 14 is added to the composition 10 during the mixing process.

Providing 66 cement 16 may be done in a conventional manner. Cements aretypically of the variety used in concrete referred to as Portlandcement, a quarried material that reacts and bonds when mixed with water.Providing 66 additives is a matter of optional design, typically by anengineer who has specified a particular construction with concrete. Forexample, additives may be provided 66 in order to provide betterworkability time, faster curing, response to temperatures, and so forth.Thus, providing 66 any particular additives may be done in view of thepresence of CFA 20 in the composition 10, or according to otherengineering directives.

Providing 67 water may be done in any manner appropriate as specified bythe process of mixing 68 the composition 10 for use. Finally, thedisposition 70 of the composition 10 may involve applying 69 thecomposition 10 to a structure, pouring it into a form or mold, such aspouring it as footings, walls, beams, or other structures. Ultimately,curing 71 prepares the composition 10 to perform its operation 59 as astructural system or a structural component in a larger system.

As described herein, curing 71 occurs as a very different process in anapparatus and method in accordance with the invention. The presence ofadditional water, at a higher w/c (water-to-cement) ratio providesaccess to water by the molecules of the cement 16 throughout theirprocesses of mixing, curing, and drying.

Referring to FIG. 5, while continuing to refer generally to FIGS. 1through 11, a chart 80 is shown containing values 82 of variousparameters 84 in an example composition 10. In the illustrated chart 80,a control 86 involves a composition 10 absent the CFA 20. Accordingly,the formulation is made as close to that of the test composition 88 ornew composition 88, in view of the addition of CFA 20, and itsimplications for the composition 10.

One will see that the control 86 included 26 pounds of cement 16, with13 pounds of water, plus 52 pounds of fine aggregate 14, and 52 poundsof coarse aggregate 12, with no lightweight aggregate, no CFA 20, and aw/c ratio of 0.5. The composition 10 was compounded to have a slump of 3inches (7.6 centimeters).

The test material 88 was compounded to have 26 pounds of cement 16, 19pounds of water, 47 pounds of conventional fine aggregate 14, augmentedby 5 pounds of CFA 20. The coarse aggregate 12 was 52 pounds, and thew/c ratio was 0.73. This w/c ratio was required in order to obtain aslump identical to that of the control 86.

It is typical of the art of construction that using a higher w/c ratiocompromises compressive strength. However, a low w/c ration createsdifficulty in workability, shortening the time, and rendering thecomposition 10 less fluid and thus more difficult to work, especially asit begins curing earlier to a solidous state. Plasticizers or “superplasticizers” are frequently added to compositions 10 having a low w/cratio (e.g., below about 0.5). Such plasticizers typically provideadditional workability of the composition 10 without increasing thewater content.

Increasing water content tends to create greater slump, meaning that theliquidous properties of the composition 10 may render it not as firm.Thus, such materials will tend to flow too easily, have the aggregate12, 14 settle too quickly rather than remaining suspended in ahomogenous mixture, and so forth.

In the test illustrated, it proved possible to obtain a higher w/c ratiowhile maintaining strength, and sustaining the level of workability,even improving it. Meanwhile, it was found to enhance internal curing ofthe composition 10.

The test material 88 was able to absorb or contain about half again morewater than the control 86. This was achieved at the same value of slump.Thus, the operational characteristics of the composition 10 in itsliquidous state are basically identical to those of the control 86. TheCFA 20 thus absorbed about twelve times its own weight in water, whichwas thereby distributed throughout the entire mix of the composition 10.Meanwhile, because the slump remained identical to that of the control86, no separation of aggregates 12, 14 out of the mix, no settlingthereof, and no localized (e.g., surface) reduction of the density ofthe concrete was experienced.

The control mix after 7 days of curing had a compressive strength of1,824 psi (pounds per square inch stress) (12.77 MPa). By day 21, thestrength had increased 460 psi (3.22 MPa) to 2,384 psi (16.69 MPa).Finally, at day 28, the usual time at which concrete is deemed to haveachieved almost its ultimate strength, and hardness. Therefore, as ofthe time after which data is usually not taken, the strength hadincreased modestly by about 116 psi (0.812 MPa) to 2,500 psi (17.5 MPa)of strength or yield stress.

Meanwhile, the test material 88 after 7 days had only 1,620 psi (11.34MPa) of compressive strength. However, at day 21, the yield stress hadincreased 800 (5.67 MPa) psi to 2,420 psi (16.94 MPa) compressive stress(strength). Finally, by day 28, the test material 88 had increased yieldstress by about 580 psi (4.06 MPa) to 3,000 psi (21.0 MPa). Thus, thestrength at day 7 was below that of the cure of the control 86. By day21, the compressive stress was only modestly (1.5 percent) higher thanthat of the control 86. However, by day 28, the compressive stress thetest material 88 could support was 20 percent higher than that of thecontrol 86.

Thus, the compressive stress test confirmed that the new material 88made in accordance with the invention provided a higher w/c ratio,providing for better workability, while yet increasing the strength ofthe concrete composition 10 cured. One interesting sidelight is that theincreased water goes into increasing the overall volume of thecomposition 10. Thus, in the test, the overall volume of concrete wasfound to increase in various samples by from about five to about tenpercent. Thus, in each cylinder tested, there was actually less cement16, less aggregate 12, 14, and overall less material.

However, the additional stress sustained belies the less material. Thishas two implications, one is that the actual stress sustained isactually higher. Meanwhile, this means that more of the composition 10may be supplied. For example, concrete (typically 9%) may be formed witha yield of from five to about ten percent more concrete (typically 9%),and at a higher compressive yield stress. Thus a traditional cubic yardof concrete in this example would have been increased about ninepercent. That is nine percent more material to sell with improvedproperties and increased workability time.

Referring to FIG. 6, another example in accordance with invention isidentified in the chart 90 or table 90. In this example, a base 93operates simply as information. That is, conventional concretetechnology provides a formulation identified as the base 93. In thiscase, the amount of water, aggregate 12, 14, and cement 16, is asindicated. One will note that the w/c ratio is only about 0.38. Thecontrol 94 has a higher slump of about 8 inches. Typically, the base 93may be expected to have a slump of less than eight inches. Typically,the base 93 may be expected to have a slump of about three inches. Thiswill vary somewhat, and thus is illustrated in brackets indicating thatit is not actually known because it may be a function of otherparameters.

The control, includes the illustrated proportions of cement 16, water,fine aggregate 14, and coarse aggregate 12. No lightweight aggregate norCFA 20 were included. The w/c ratio was thus 0.51 resulting in a slumpof about eight inches (20 centimeters). The lightweight aggregate (LWA)material 96 used a newer technique of adding in with the conventionalfine aggregate 14 a lighter weight aggregate, which may be formed of anorganic material, such as a plant material, or from a highly porous rockmaterial that has much more space in capillary voids to absorb water.

In this embodiment, the LWA material 96 included the same amount ofcement 16, 15 pounds of water, slightly more than the control 94, and40.2 pounds of fine aggregate 14. Meanwhile, the coarse aggregate 12 wasthe same for all materials 94, 96, 98 in the test. However, LWA materialwas 13.4 pounds, adding to an overall constituent mass of 53.6 poundsfor all of the fine aggregate 14 in the composition 10. The water addedprovided a w/c ratio of 0.57 needed in order to achieve the same slumpas the other materials 94, 98 in the test.

The new test material 98 included the same amount of cement 16, agreater amount of water than either the control 94 or the LWAcomposition 96, and much more water than the conventional base 93, bymore than double. The result was that fine aggregate 14 was reducedslightly, in order to accommodate 3.2 pounds of the CFA 20. This slightamount of CFA 20 added to provide a total of 54.6 pounds of total fineaggregate 14, including the CFA 20 as a portion thereof. The resultingw/c ratio was 0.79, about half again as large as the w/c ratio of thecontrol 94 and LWA composition 96. However, this was more than doublethe w/c ration of the base 93 of conventional concrete.

The sand used as fine aggregate 14 was the same in all mixes. The amountof water used is different simply because workability was desired as afixed parameter and the ability to pour the composition 10 is not only agood comparator but a convenience in the test. The various ratios of w/cwere chosen to achieve approximately identical slump between all themixes used. The additional water required was simply that needed toachieve the consistent values of that same effective operationalproperty of slump.

One striking observation is how much more water was required by the newcomposition 98 in order to achieve the slump value. This is due to thevolume of the water absorbed by the particles 32 of the polymer 30coating each of the CFA granules 22.

Hereagain, this was observed to increase the volume of the liquidouscomposition 10 by nine percent. However, the cured sample increased involume by 13 percent. Thus, nine percent more concrete is available inthe mixture of a composition 10 in accordance with the invention.However, less shrinkage occurs in the ultimate structure that is left tooperate 59. Thus, the structure was larger by 13 percent. Thistranslates to increased section modulus. Section modulus controlsstiffness and strength.

Strength is actually stress, a force per unit area. That number does notchange, but the actual value or strength of a structure changesaccording to how far away from the neutral axis (a term of art fromengineering meaning the approximate or effective midline at which thereis no stress, compressive or tensile, in bending the beam or structure).Thus, a 13 percent increase in size provides a commensurate largerdimension, with extra stiffness and strength of a particular structurein bending. Thus, the supported stress level is benefitted.

In the illustrated example, the samples were molded in a standardconcrete test mold and maintained at room temperature and conditions ina laboratory. The cement 16 was a type I-II Cemex™ Portland cement 16. AQuikrete™ all purpose gravel (#1151) was used as the coarse aggregate12. Applicants provided the CFA 20.

All testing was done in a conventional loading apparatus and all threesamples were used as per the test mixing procedure and the constituentproportions illustrated. Multiple samples were made in order to obtainrepeatability in the results. The samples were tested according to ASTMStandard 469 (American Society for Testing of Materials), forcompression strength. Flexural strength was tested according to ASTMStandard C78. Tensile strength was tested according to ASTM StandardC496. Likewise, water absorption or permeability was tested, andshrinkage was evaluated.

Two types of curing were used in the studies. Part of the test was a wetcure in which samples were cured in water. Another was internal orself-curing in which no water was added to the surface, but conventiontechniques were used to rely on internal curing with only the watercontent available within the composition 10.

Referring to FIG. 7, the test data is illustrated for the wet curedcomposition 10. One will note that the chart 100 shows several valuescorresponding to the various parameters 104 reflecting strength or yieldstress. At day seven, the control 94 sustained 2,311 psi (16.177 MPa) ofcompressive stress. The lightweight aggregate 96 sustained 2,405 psi(16.835 MPa) of stress. Meanwhile, the new material 98 in accordancewith the invention sustained only 2,330 psi (16.31 MPa).

Meanwhile, at 21 days, the various material samples 94, 96, 98 were muchcloser to one another. At day 28, the compressive stress sustained wasagain almost identical between the materials. The control 94 wasslightly less than the LWA material 96, and the new material 98.Flexural strength was virtually identical, within a reasonable range ofexperimental error. Similarly, the split tension was likewise almostidentical. In each case, the new material 98 was slightly better thanthe control 94, but not significantly so. Thus, while providing a muchgreater workability, the composition 10 in accordance with the inventiondid not provide any downside, and provided a nine percent increase involume of the liquidous composition 10 and a 13 percent increase involume in the solid state.

Referring to FIG. 8, the sample materials were left to dry and curebased on whatever water was present. This is referred to as internalcuring or self-curing. The results are shown in the table 101. Here, atday seven, the control 94 has not had the additional water available atits “outermost fiber” (as the term applies to section modulus andbending stress) or outer surfaces. Thus, it is perhaps not surprisingthat the compressive strength is reduced below that of the wet cure. Thesame is true of the LWA material 96 and the new material 98. By day 21,both of the water-bearing samples including the LWA sample 96 and thenew material 98 are outstripping the compressive stress sustained by thecontrol 94. By day 28, the LWA material 96 has failed to significantlyadvance beyond the control 94. Improvement is present but only slight.

By contrast, the new material 98 is on the order of about 25 percentstronger. Flexural strengths are comparative, with the new material 98being about ten percent stronger than the control 94. The LWA material96 is slightly stronger than the control 94, and still substantiallyweaker than the new material 98. Similarly, the split tension, largely ameasure of the same tensile strength property, but in a differentconfiguration of direct tension rather than the tension of flexure orbending, provides a similar result.

Referring to FIG. 9, the data from the chart 101 is illustrated in thechart 105. The x axis 106 represents time in days, while the y axis 108represents the strength, this is represented as a fracture due to stressor yield stress (failure stress) represented as a force per unit area.This may be represented in pounds per square inch (psi), MegaPascals(MPa), or the like. In the illustrated test results, one will see thatthe curve 116 of the test material 98 higher than both the curve 112representing the control 94 and the curve 114 representing the LWAcomposition 96. It is not clear that the curve 116 is declining at thesame rate as the curves 112, 114.

For example, one will note that the number of points is not sufficientto necessarily fit higher order curves to the data accurately.Additional data points beyond day 28 are not typically taken. However,it is not clear that the strength has ceased its increase. Between days21 and 28 it is quite clear that the rate of increase of strength orstress support in the control 112 and LWA composition 114 has decreased.Thus, not much additional strength can be expected. In contrast, in newmaterial 98 appears to not be finished with increasing its strength.

Referring to FIG. 10, the porosity or permeability was tested by placingthe cured materials into water over a period of time in order todetermine the weight gain. Weight gain represents how much water isabsorbed into voids in the concrete.

For example, permeability represents not only the amount of voidfraction within a solid material, but the ability of water to passthrough it. This property allows water and other chemicals to penetrateconcrete and render it susceptible to attack by chemical changes,corrosion of reinforcing steel, breaking by frost damage,alkali-aggregate reactivity, and the like. Voids in concrete play amajor role in increasing permeability and are typically the result ofevaporation of water not utilized in hydration (chemical reaction) ofthe cement 16 as it turns from an unconsolidated powder to a solid.

Likewise, inefficient consolidation of the fresh concrete may leavevoids due to lower slump where the concrete is too stiff and thereforaggregate is not as free to move. For example, this is one reason whyvarious additives may be added to increase the lubricity of theliquidous constituents in a composition 10 while being poured andsettled.

The samples cured in water baths were weighed to observe the wateruptake. The data was used to get an indirect indication of thepermeability of the different samples. The control 94 gained 0.1 poundsin the sample of the particular size tested (a standard 6x3 concretetest mold). Meanwhile, the new material 98 or the CFA augmented material98 absorbed 0.03 pounds. Meanwhile, the LWA augmented material 96absorbed 0.11 pounds of water.

One will note that the control 94 and the LWA augmented material 96performed about the same within about ten percent of one another.However, less than ⅓ as much water was absorbed by the CFA sample.

The w/c ratios used in this experiment are not necessarily thoserecommended for the majority of concrete work because they maynegativity affect strength, permeability, and shrinkage. However, thisdoes suggest that the presence of the polymer 30 may tend to providesmaller voids, and also possibly less connectivity between voids.

Moreover, near the surface of a solid material, any intrusion by waterwill eventually be halted, and rather quickly so, by the expansion ofthe polymer 30 remaining in the voids near the surface. Each of thesubstrates 22 has a thin layer 18 of the polymer 30 that keeps elementsfrom entering the matrix of the solid. It is understood that hydrogenbonding between the polymer 30 and water forms the gel-like substancethat was observed in inspection of the tested materials. Thus, the useof SAP or other polymers 30 decreases permeability by excess water fromrain, snow, immersion, spray, or the like.

Referring to FIG. 11, shrinkage was also evaluated. Cracking in concretein many instances is due to dimensional changes during the curingprocess. For example, near the surface, water is not only consumed in achemical reaction with cement 16 throughout a concrete structure, but acertain amount of water is evaporated at the surface. That evaporatedwater is both unavailable during the cure of the cement 16 in itsongoing chemical reaction during the cure process, but also results inshrinkage, prematurely, near the surface, resulting in small cracking.

Thus, plastic shrinkage happens within the first few hours after mixingdue to the chemical reaction. Autogenous shrinkage is shrinkage due tothe hydration of process or water uptake inside. Plastic shrinkage is“plastic” in the engineering sense that it does not result in yieldingof the material. The material shrinks and does so plastically. Thatinduces no stress, and does not result in fracture. On the other hand,autogenous shrinkage results from the chemical reaction inside and theuptake of water by the cement 16. This results in a certain amount ofshrinkage of the bulk volume of material. Meanwhile, shrinkage, or waterlost to atmospheric evaporation was not participating in the chemicalreaction with the cement 16, but is lost by the permeability of theconcrete to the surrounding atmosphere during the process of curing anddrying. Thus, drying shrinkage is likewise real and results inshrinkage.

There is also some amount of carbonation shrinkage due to the chemicalreaction of carbonation over extremely large periods of time. It hasbeen found here in the chart 120 of FIG. 11 that over the timeillustrated on the x axis 106, the actual micro strain in length perunit length, a dimensionless parameter, and thus correct for any systemof units, is different for each of the materials 94, 96, 98.

For example, the values 122 of strain 122 as represented on the y axis108 are illustrated in the curves 124, 126, 128 the control curve 124shows that substantial strain or change in dimension exists in thecontrol 94. The LWA-modified material 96 is much improved, due to itsadditional availability of water in the capillaries in the lightweightaggregate. Meanwhile, the CFA-augmented material 98 provides the leaststrain, at the latest measurement at 28 days. However, intermediate thattime, and the start date, at seven days, the LWA-modified material 96actually had less strain. This seems to indicate something about therate of release of water as well as total amounts in the differentmaterials 96, 98.

When a super absorbent polymer (SAP) 30 was added by a coating layer 18on a coated fine aggregate (CFA) 20 configured as a granule 22 orsubstrate 22 having the coating 18, the overall composition 10 absorbedmore water while maintaining the same value of slump, which reflects theworkability of such a composition 10. The composition 10 appeared toabsorb water both as a matter of surface tension among all theconstituents, as well as by absorption through a polymer 30 in thecoating 18 of the CFA 20.

It appears that hydration is the key to increase strength and is drivenby the availability of water for chemical reactions required by themolecules of the cement 16 material. Beyond an initial seven day curingduration, significant improvement in compressive strength for a drycured concrete (internally cured or internal cure) is not available.Whatever fluid was available inside the sample has been used. In theimprovements in accordance with the invention, swelling and absorptionof water by a polymer 30 through osmotic uptake appears to rely on thehigh concentration of ions within the SAP 30. Elastic forces within thepolymer 30 itself keep the swelling within certain limits, howeverlarge.

Desorption of water presents a balance between the cement 16 constitutedas a paste and the polymer 30. Meanwhile, capillary pressures appear toaid in the release of water. Of course, capillary pressures areparticularly low but do increase somewhat with age.

Lightweight aggregate 96 shows that the contained water is releasedwithin about three to seven days after pouring. Polymers 30 used inprevious mechanisms or previous configurations have been inconsistentfor a variety of apparent reasons. Polymers alone do not disperse well,they tend to become tacky and agglomerate with one another. They tend toabsorb too much water forming large voids once they become desiccated.This causes stress concentrations resulting in reductions of compressivestrength and crack formation due to surface desiccation.

It appears that coating the substrate 22 with the polymer 30 in a dust32 or powder 32 configuration overcomes the previous problems. First ofall, the weight of a granule 20 of a CFA 20 is dominated by thesubstrate 22 itself, which amounts to some version of an aggregate 14.Thus, mixing is readily effective to distribute the polymer 30 with afraction of fine aggregate 14 constituted as a CFA 20.

More water is available in the mix, and the holders of water, theparticles 32 of the polymer 30 are more dispersed, distributed morewidely, more uniformly, and in much smaller quantities of polymer 30.Moreover, even within each CFA 20 constituted as a single granule 20,the relative sizes of the particles 32 of the polymer 30 may beconsiderably smaller than those causing “inclusions” in concrete inprevious experiments.

More water (higher w/c ratio) is absorbed for the same value of slump,thus providing more water during cure, equivalently excellentworkability, with even greater workability time frames. Thus, slumpcontrols how workable the concrete is at the moment that work begins.However, the longevity of that workability is extraordinary by using theCFA 20 in accordance with the invention.

Voids must continue to exist in the layer 18, once the concrete has beenfully cured and desiccated. However, the dimensions of such voids are sosmall, and so thoroughly distributed, as even only a fraction of aboutten percent or 1/10 of the total fine aggregate 14 is constituted in theCFA 20. Meanwhile, fine aggregate 14 only constitutes half the totalaggregate.

Also, the significance of the voids diminishes by their small size andwide distribution. Moreover, localized failures about a single granule22 should appear to be minimized from and restricted from propagatingdue to the fact that there is a solid within every void, namely thegranule 22 of sand or aggregate 14 that forms the core of a CFA 20. Thisis a stark contrast to large voids left by SAP added directly toconcrete mixes.

The rate at which water is released is reflected in the fact that thecomposition 10 in accordance with the invention contains 50 percent morewater in one example yet provides the same slump. This means that lessfree water exists to fluidize and lubricate the aggregate 12, 14 in thecomposition in its liquidous configuration. However, over time, thatsame water is necessary or beneficial for augmenting reaction of thecement 16 in its own bonding. It is local and available. The migrationpath is very short. The mean distance between adjacent CFA 20 particles20 as individual granules 20 seems comparatively small. Simply lookingat the ratios in the samples for the materials illustrates that thecement 16 is the least of the dry materials. Only the polymer 30 is lessin the compositions 10 in accordance with the invention.

The availability of water during the reaction process is illustratedamply in the test data by the improved strain rates observed. Lessstrain indicating less shrinkage correlates to the region where asubstantial increase is obtained in compressive strength.

Permeability appears to be improved by two mechanisms. First, becausethe layer 18 constitutes such a small fraction of the overall volume ofeach granule 22 of the CFA 20 (the substrate 22 dominates the volumefrom a very thin layer 18 coats it), the cement 16 tends to close inaround each granule 22. In contrast to other systems, large voids andintraconnectivity between voids is thereby avoided.

Moreover, water that would ordinarily be free water within the matrix ofaggregate 12, 14 and the cement 16, resulting in drying out and exitingto leave behind voids, has instead been wrapped around the outside layer18 of each CFA 20. Thus, free water may actually be reduced yetavailable for curing.

Finally, the layer 18 remains behind, forming the void but alsocontaining the polymer 30 that was originally configured as particles 32or powder 32. Upon rehydration from an outside source (absorption ofwater through the pervious matrix), the polymer 30 in the layer 18 willexpand again and absorb water when the water is present. This results inan immediate damming of water from further hydrating the interior of astructure. Thus, there is less porosity or perviousness to liquids andchemicals that may attack concrete in weathered, underwater, or otherhydrated environments.

Meanwhile, the water volume that is added results in not only its ownvolume, but additional space amounting to about nine percent of theoverall volume of the resulting composition 10. Moreover, after curing,that volume percentage increase is about 13 percent over the control 94.Thus, the liquidous composition 10 is nine percent greater in volume,and shrinks less, resulting in a net 13 percent greater volume in acured sample over a comparable control 94.

The present invention may be embodied in other specific forms withoutdeparting from its purposes, functions, structures, or operationalcharacteristics. The described embodiments are to be considered in allrespects only as illustrative, and not restrictive. The scope of theinvention is, therefore, indicated by the appended claims, rather thanby the foregoing description. All changes which come within the meaningand range of equivalency of the claims are to be embraced within theirscope.

What is claimed and desired to be secured by United States LettersPatent is:
 1. A composition comprising: coarse aggregate comprisingrocks of a comparatively larger size; fine aggregate comprising granulesof sand having an average maximum dimension substantially smaller thanthe coarse aggregate; cement; and polymer coated aggregate comprising aportion of the fine aggregate having the granules individually coatedwith discrete, individual, and discontinuous particles of a powdercomprising a water-absorbing polymer.
 2. The composition of claim 1,wherein the polymer coated aggregate constitutes less than about onetenth of the fine aggregate.
 3. The composition of claim 2, whereinpowder is bound by a binder to the granules individually, as asubstrate.
 4. The composition of claim 3, wherein the powder comprisesindividual particles, each having an outer portion facing away from thesubstrate, and a contact portion in contact with at least one of thebinder and the substrate, the outer portion remaining dry continuallyfrom before application to the substrate until mixing into thecomposition.
 5. The composition of claim 4, wherein the powder is formedof a polymer selected from an acrylamide, an acrylamide co-polymer, apolyacrylamide (PAM), and a super absorbent polymer (SAP).
 6. Thecomposition of claim 5, wherein the cement is constituted in a fluidphase flowable to lubricate the coarse aggregate and fine aggregate, thecement and fine aggregate substantially filling interstitial spacebetween the rocks of the coarse aggregate.
 7. The composition of claim 5further comprising a binder binding the contact portions of the powderto the substrate.
 8. The composition of claim 7, wherein the polymer iswater soluble and separable from the substrate by dissolving upon beinghydrated by a portion of the water subsequently releasable by thepolymer to provide at least one of additional water for workability,water for reaction of cement, water for reduction of surface shrinkage,and slowing of drying of the composition.
 9. The composition of claim 8,further comprising, in cured state, voids created by dehydration of thegranules and having an average maximum dimension sufficiently small tobe effective to maintain strength properties effectively equal to thoseof the composition absent voids.
 10. The composition of claim 1, whereinthe proportions of constituents, proportioned in parts by weight,further comprise about two parts cement, about four parts fineaggregate, about four parts coarse aggregate, and about 1.5 parts water,wherein about ten percent of the fine aggregate further bears a coatingof the polymer.
 11. The composition of claim 1, constituted from partsproportioned by weight, wherein: the cement constitutes an amount offrom about one and a half to about two and a half parts; the fineaggregate constitutes from about 3 to about 5 parts; the coarseaggregate constitutes from about 3 to about 5 parts; the waterconstitutes from about 1.25 to about 2 parts.
 12. A method of combiningconstituents, the method comprising: selecting a coarse aggregatecomprising rocks of a comparatively larger size; selecting a fineaggregate comprising granules of sand substantially smaller than therocks; selecting a cement; selecting a polymer comprising a powderhaving particles, dry, discrete, and comminuted to a size smaller thanthe granules; providing a coating comprising a dry dust of the powderadhered, as distinct and individual particles, by a binder to selectedindividual granules added in to become a portion of the fine aggregate;mixing the constituents with water.
 13. The method of claim 12, wherein:the water, cement, and fine aggregate effectively completely fillinterstitial space between the rocks of the large aggregate; the coatingis a hydrophilic material; and the method further comprises casting themixture into a restraint effective to mold the mixture to a shape. 14.The method of claim 13 further comprising: providing, by the coating,water into the cement effective to maintain fluidity of the mixture fora period greater than one and a half hours; and curing the constituentsto a level of compressive strength undiminished by the water.
 15. Themethod of claim 14, wherein the coating is a water soluble polymerseparable from the granules by dissolving with the water, to an extenteffective to extend the time to greater than 2 hours.
 16. The method ofclaim 12 further comprising curing by the cement from a liquidous stateto a solid state comprising voids created by a difference in volumebetween the particles containing absorbed water, and the particlesdehydrated during curing.
 17. The method of claim 16, further comprisingproviding by the polymer to the cement additional water for increasingthe amount of chemical hydration reaction with the cement.
 18. Themethod of claim 12, wherein the polymer is a water soluble, syntheticpolymer.
 19. The method of claim 18, wherein the synthetic polymerfurther dissolves proximate the granules sufficiently to separate fromthe granules during the mixing.
 20. The method of claim 12, wherein thepolymer is selected from polyacrylamide, a co-polymer of at least one ofan acrylate, acrylic, and acrylamide, an acrylamide compound, a superabsorbent polymer.